A DC to AC converter, i.e. an inverter, is typically used when connecting a solar power plant to an electricity grid. Refinements in insulation systems and the evolution of practice in the art have led to bipolar (i.e. two-level) 1.5 kV solar cell arrays connected in such a way that a net 3 kV link is used to collect photo-generated current from the solar power plant. Such arrays output power that is likely in the megawatt regime. This increase in power throughput and voltage typically leads to increased costs.
Furthermore, where such arrays exist, uneven irradiance reduces to the annual energy yield. Therefore, the ability to separately determine the optimal voltage from a positive sub-array and from a negative sub-array is needed in order to recapture energy that would otherwise be lost when the solar array is restricted to a single voltage.
Lastly, typical solar power converters optimized for a 3-wire grid-side connection do not take into account the complexity of controlling a positive bus current independently of a negative bus current while providing independence in bus voltage. As such, there is a need to control an optimized forward sequence current in quadrature (D/Q) independence, especially when the converted currents are recombined in the high-voltage winding of a transformer and fed to the electricity grid.